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PDBsum entry 1ed7
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Contents |
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* Residue conservation analysis
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References listed in PDB file
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Key reference
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Title
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Solution structure of the chitin-Binding domain of bacillus circulans wl-12 chitinase a1.
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Authors
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T.Ikegami,
T.Okada,
M.Hashimoto,
S.Seino,
T.Watanabe,
M.Shirakawa.
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Ref.
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J Biol Chem, 2000,
275,
13654-13661.
[DOI no: ]
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PubMed id
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Abstract
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The three-dimensional structure of the chitin-binding domain (ChBD) of chitinase
A1 (ChiA1) from a Gram-positive bacterium, Bacillus circulans WL-12, was
determined by means of multidimensional heteronuclear NMR methods. ChiA1 is a
glycosidase that hydrolyzes chitin and is composed of an N-terminal catalytic
domain, two fibronectin type III-like domains, and C-terminal ChBD(ChiA1) (45
residues, Ala(655)-Gln(699)), which binds specifically to insoluble chitin.
ChBD(ChiA1) has a compact and globular structure with the topology of a twisted
beta-sandwich. This domain contains two antiparallel beta-sheets, one composed
of three strands and the other of two strands. The core region formed by the
hydrophobic and aromatic residues makes the overall structure rigid and compact.
The overall topology of ChBD(ChiA1) is similar to that of the cellulose-binding
domain (CBD) of Erwinia chrysanthemi endoglucanase Z (CBD(EGZ)). However,
ChBD(ChiA1) lacks the three aromatic residues aligned linearly and exposed to
the solvent, which probably interact with cellulose in CBDs. Therefore, the
binding mechanism of a group of ChBDs including ChBD(ChiA1) may be different
from that proposed for CBDs.
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Figure 2.
Fig. 2. Summary of the structure information obtained in
the NMR experiments. A, summary of the sequential and medium
range NOE connectivities, secondary structures, chemical shift
indices, amide hydrogen exchange rates, 3J[HNH  ]coupling
constants, and solvent accessibility values for ChBD[ChiA1]. The
NOE connectivities are represented by bars, the size of which
indicates the NOE intensity (strong, medium, or weak). The
notation d[ N(i, i
+ 1)], for example, represents the connectivity between the  proton
resonance of a residue (i) and the amide proton resonance of the
subsequent residue (i + 1) in the sequence. Amide protons that
were exchanged slowly at pH 6.0 and 298 K are indicated. The
residues with life times of >0.5 h and <4 h are indicated by
open circles, >4 h and <18 h by half closed circles, and >18 h
by closed circles. The three-bond scalar coupling constants
between spins 1HN and 1H (3J[HNH
]) of
<4.9 Hz are indicated by open boxes, >4.9 Hz and <8.5 Hz by
one-third closed boxes, >8.5 Hz and <10.0 Hz by two-thirds
closed boxes, and >10.0 Hz by closed boxes. The chemical shift
indices (CSI) (38) are plotted for 1H resonances.
Upper bars, +1; lower bars,  1;
horizontal lines, 0. The solvent accessibility was calculated
with the program MOLMOL (36) for the side chain of each residue
and is shown by the bar height ranging from 0 to 60%. The figure
was produced with the program VINCE (Rowland Institute for
Science). B, the distance information defining the  -sheets of
ChBD[ChiA1]. The intra- and interstrand NOEs are indicated by
arrows. The hydrogen bonds used for the structure calculations
are indicated by dotted lines. The residues constituting the
-strands are
labeled with black boxes. C, schematic diagram of the -strands of
ChBD[ChiA1]. The diagram is drawn in the same direction as in B.
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Figure 6.
Fig. 6. The residues that may interact with chitin. The
side chain atoms of these residues are shown in a space-filling
model on a ribbon representation of ChBD[ChiA1] in stereo.
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The above figures are
reprinted
by permission from the ASBMB:
J Biol Chem
(2000,
275,
13654-13661)
copyright 2000.
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